Method for treating polymeric substrates prior to plating employing accelerating composition containing an alkyl amine

Abstract

A process for treating a polymeric plastic substrate to render it receptive to electroless plating including the steps of etching the substate, rinsing and activating the etched substrate with an acidic tin-palladium complex, rinsing and thereafter accelerating the activated substrate employing an improved aqueous accelerating solution containing an aqueous soluble compatible substituted alkyl amine. The improved accelerating solution is stable, easy to control, tolerant to metallic impurities present in the solution, inhibits rack plating and is of versatile use.

What is claimed is: 
     
       1. In a process for treating a polymeric plastic substrate to render it receptive to electroless plating including the steps of etching the substrate with an aqueous acid solution containing hexavalent chromium ions, rinsing and activating the etched substrate with an acidic tin-palladium complex, rinsing and accelerating the activated substrate, the improvement comprising contacting the activated substrate during the accelerating step with an aqueous acidic accelerating solution having a pH of about 0 to about 7 and containing an aqueous soluble compatible substituted alkyl amine present in an amount effective to complex substantially all of any contaminating cupric and ferric ions present and to extract any residual tin constituents present on the surface of the activated substrate, an anion of a mineral acid or alkali metal salts thereof present in an amount up to about 120 g/l, said substituted alkyl amine corresponding to the following structural formula: ##STR3## Wherein: R 1  is an organic radical ##STR4##  in which x and y=1 to 4; R, R 2  and R 3  is H or --CH 2  ] z  X in which z=1 to 6 and X is --OH, --SO 3  H, --COOH, --NH 2 , halide, --CH 3 , or --OCH 3 , as well as the alkali metal salts of the foregoing.   
     
     
       2. The process as defined in claim 1 in which said substituted alkyl amine is present in an amount of from about 0.001 to about 100 g/l. 
     
     
       3. The process as defined in claim 1 in which said substituted alkyl amine is present in an amount of about 0.01 to about 10 g/l. 
     
     
       4. The process as defined in claim 1 in which said anion is selected from the group consisting of a halogen, sulfate, bisulfate and mixtures thereof. 
     
     
       5. The process as defined in claim 1 in which said aqueous accelerating solution further contains an effective amount of an aqueous soluble bath compatible reducing agent to reduce any residual hexavalent chromium ions present to the trivalent state. 
     
     
       6. The process as defined in claim 5 in which said reducing agent comprises a hydroxylamine salt. 
     
     
       7. The process as defined in claim 6 in which the hydroxylamine salt is present in an amount of about 0.005 to about 10 g/l. 
     
     
       8. The process as defined in claim 7 in which the hydroxylamine salt is selected from the group consisting of hydroxylamine hydrochloride, hydroxylammonium acid sulfate, hydroxylammonium sulfate and mixtures thereof. 
     
     
       9. The process as defined in claim 1 in which said anions are present in an amount of about 40 to about 90 g/l. 
     
     
       10. The process as defined in claim 1 in which said substituted aliphatic amine is ethylenediaminetetraacetic acid as well as the mono, di, tri and tetra alkali metal salts thereof.